1. Field of the Invention
An adjustable chair for human dental or medical treatment, beauty parlors, barber shops, or the like.
2. Description of the Prior Art
As is generally known, almost all of dental treatments today are with the patient being treated in lying position. That means that the lying position is easier for treatment than is sitting up position, and is also comfortable for the patient as well; yet, a complete satisfaction was still unobtainable with the conventional chair.
As has been known, the underseat of a dental chair in the past was constructed in a single configuration, in which from the hip section to the leg section of the structure was altogether in one. The part where the legs were to be placed was tilted somewhat, for example downwards. And in addition, although connected to the base plate, this underseat was set up to be capable of making vertical motion. As for the underseat itself, it was not operative. However, in such conventional methods of underseat fabrication, when the upper half of the patient's body was in contact with the backrest in straight or near straight position, there was no problem; but when the backrest was tilted, the lower half of the patient's body, from the area of the knee joint to the hip section, was tilted in one plane. Therefore, when the patient was undergoing a longer period of treatment, 10-20 minutes for example, under the condition especially when the backrest was tilted to a greater degree, for example 60.degree.-90.degree., there was pain accompanying the patient, particularly in his abdominal muscles.
The prior art includes motor-driven configurations for adjusting the components of a dentist's chair relative to one another. Typical of the prior art is U.S. Pat. No. 3,027,194 which discloses a headrest with a curved shank that has several dimples formed therein. The dimples cooperate with spring-loaded balls to define the locked position for the headrest relative to a vehicle seat. U.S. Pat. No. 3,542,428 discloses an adjustable headrest which has a curved linear member that enables the same to be adjusted relative to the back of an automotive seat. Other prior art of interest includes U.S. Pat. Nos. 694,683; 910,357; 2,481,133; 2,987,116; 3,578,379; and 3,836,197.